1. Field of Invention
This invention relates to radar receivers that overcome the effect of interfering noise sources and pulse sources and particularly to a receiver that is compatible with both coherent side lobe cancellation and side lobe blanking operation so as to blank out a minimum of possible target signals.
2. Description of the Prior Art
Coherent side lobe cancellers (CSLC) are designed primarily to cancel continuous jamming such as noise jamming or CW (Continuous Wave) jamming. Also incorporated with the CSLC circuit in many receiver systems is a side lobe blanking (SLB) circuit which is used primarily to blank interfering or jamming pulses which are of such a short time duration that the CSLC circuit cannot acquire and cancel these pulses. The coherent side lobe cancellation usually is performed in conventional systems immediately after the second converter and prior to the matched filter in the receiver, while the side lobe blanking is performed at the video output of the receiver. As a result, these two processes occur sequentially in the receiver processing chain and the conventional side lobe blanking circuit has been found to also blank the noise jammer even after the CSLC circuits have acquired and are cancelling the jamming signal. It would be a substantial improvement to the art to provide a compatible type system that allows the side lobe blanking circuit to blank only the leading edge of a noise jammer so that after the CSLC circuits have acquired the jammer, the SLB circuits are automatically deactivated except that the SLB circuits will still blank any pulse interference larger than the noise jamming signal that occurs during the jamming interval.